GROWTH AND DEVELOPMENT OF WHITE CLOVER (TRIFOLIUM-REPENS L.) AS INFLUENCED BY P AND K NUTRITION

The effects of varying P and K supplies on the growth and morphology o f white clover were investigated in a pot experiment. Plants were trea ted with three rates of potassium (K) and four rates of phosphorus (P) in factorial combination, and five harvests were taken between August 1993 and February 1994. During establishment, shoot and leaf developm ent were more adversely affected by P than by K deficiency but, by the final growth period, K deficiency was the more limiting to growth, ca using dramatic reductions in leaf area index (LAI), numbers of growing points, and stolen and root masses. The adverse affects of K deficien cy on shoot development were attributed to the curtailment of petiole and lamina expansion which have major requirements for K. It was noted that, under K deficiency, proportionately less assimilate was partiti oned to leaf production than to stolen and root growth; this may be an adaptation enabling K-deficient plants to exploit nutrient supplies i n adjacent localities. The results suggest that, provided white clover can withstand 'moderate' P stress during establishment, its persisten ce in swards will probably be limited more by K deficiency than by low or inadequate P supplies. However, because the experiment was conduct ed outside the normal growing season and with only a single white clov er cultivar, it is inappropriate to make any generalizations regarding the effects of P and K nutrition on white clover in the field. (C) 19 98 Annals of Botany Company.